Method of detection of signals using an adaptive antenna in a peer-to-peer network

ABSTRACT

An adaptive antenna signal identification process to provide increased interference rejection in a wireless data network such as a wireless Local Area Network (LAN). The adaptive antenna is located at an access point and can be steered to various angle of arrival orientations with respect to received signals. Associated radio receiving equipment utilizes two distinct signal detection modes. In a first mode, the directional antenna array is set to have an omni-directional gain pattern. In this mode, certain identification parameters of an initial portion of a received signal are detected, such as a source identifier. If the received signal has not been previously detected, then the antenna array is scanned determine a direction setting that provides a best received signal metric. Once the best directional setting for the received signal, that setting is saved for future use in receiving the same signal. If the received signal has been previously detected, the system instead will steer the directional antenna to the last known best direction for reception for the particular detected signal. As further portions of the same signal are received, such as payload portions of a data frame, the directional antenna array can continue to scan potential new best angles. When the invention is deployed in a relay function, where messages received from a first node are to be forwarded to a second node, the recorded direction of its best reception is retrieved for the second node and used when the antenna array is used to transmit the signal to the second node. Storage of the best antenna angle for propagation to neighbor nodes can be handled by control functions in a manner that is analogous to other router lookup tables, such as being contained in a lookup table that stores IP addresses.

BACKGROUND OF THE INVENTION

This invention relates generally to wireless data transmission systemsand in particular to a technique for using directional antennas in suchsystems.

In corporate enterprises, wireless Local Area Networks (LANs) areusually implemented as a final link between existing wired networks anda group of client computers. Today's business environment ischaracterized by an increasingly mobile work force, who spend much oftheir time working in teams that cross functional, organizational andgeographic boundaries. Often their most productive times occur inmeetings that take place away from their desks. Users of portablecomputing equipment therefore need access to their data files throughnetworks that reach far beyond their personal desktops. Wireless LANsfit well into this environment, providing much needed freedom in networkaccess to mobile workers. Such networks provide access to informationfrom anywhere within an enterprise, such as from a conference room,cafeteria, or even a remote branch office. Wireless LAN connectivityaffords access to the full resources and services of a corporate networkacross a building or campus setting. As such, they are on the verge ofbecoming a mainstream solution for a broad range of businessapplications.

One critical issue affecting the effectiveness of wireless LANdeployment has been the historically limited throughput available withsuch equipment. The 2 Mega bits per second (Mbps) data rate specified bythe original Institute of Electrical and Electronics Engineers (IEEE)wireless LAN standard 802.11, dated 1997, is now considered to be tooslow to support most business requirements. Recognizing the need tosupport additional higher data rate transmissions, the IEEE recentlyratified an 802.11b standard that specifies data transmission speeds ofup to 11 Mbps. With the 802.11b standard, wireless LANs are expected tobe able to achieve throughput comparable to the legacy wired Ethernetinfrastructure. Emerging wireless networking systems that promise toprovide comparable data speeds include Home RF, BlueTooth, and thirdgeneration digital cellular telephone systems.

In these peer-to-peer networks, the individual computer nodes operate ina same frequency communication network. That is, these systems utilizesignal modulation schemes such as Code Division Multiple Access (CDMA)wherein a number of end nodes are actually transmitting on a same radiofrequency carrier at the same time. Such systems may experiencesignificant quality degradation due to the interference of equipmentthat is not participating in system communication processes. Forexample, wireless LAN systems typically operate in unlicensed radiofrequency bands. Other types of radio equipment operate in these bands,equipment that is not required to operate in accordance with thepromulgated LAN standards, and therefore, cannot be controlled. Thesetransmissions from such non-system nodes can significantly reduce theperformance of a wireless LAN. As data rates increase, susceptibility tosuch interference also increases accordingly.

Various other problems are inherent in wireless communication systems.One such problem is the so-called multipath fading problem whereby aradio frequency signal transmitted from a sender (either a base stationor another mobile subscriber unit) may encounter interference enroute toan intended receiver. The signal may, for example, be reflected fromobjects such as buildings that are not in a direct path of transmissionbut then are redirected as a reflected version of the original signal tothe receiver. In such instances, the receiver actually receives twoversions of the same radio signal: the original version and a reflectedversion. Since each received signal is at the same frequency but out ofphase with one the other due the longer transmission path for thereflected signal, the original and reflected signals may tend to canceleach other out. This results in dropouts or fading of the receivedsignal.

Radio units that employ single element antennas are highly susceptibleto such multipath fading. A single element antenna has no way ofdetermining a direction from which a transmitted signal is sent andcannot be tuned or attenuated to more accurately detect or receive asignal in any particular direction operating by itself. It is known thatdirectional antennas can therefore alleviate both the multipath fadingand similar problems to some extent.

SUMMARY OF THE INVENTION

The present invention is used in a wireless data network that employs anadaptive directional antenna array to assist in isolating physical layerradio signals transmitted between system nodes. A controller canconfigure the antenna apparatus to maximize the affect of radiatedand/or received energy. Specifically, the antenna apparatus typicallyincludes multiple antenna elements and a like number of adjustabledevices such as phase shifters, passive elements, or the like, that maybe independently changed to effect the phase of received and/ortransmitted signals. The antenna apparatus can therefore be oriented orsteered to various angle of arrival orientations with respect totransmitted or received signals.

The adaptive antenna makes use of radio receiving equipment thatutilizes two distinct signal detection modes. In a first receive mode,the controller sets the antenna to an omni-directional setting. Thismode is used when a received signal has not yet been identified or thelink layer connection established. A second receiver mode, in which theantenna is set to a specific directional angle, is used after a receivesignal has been identified or a link layer connection established.

According to an embodiment of the invention that uses identification ofthe received signal to determine the antenna array mode, a multi-stepprocess is employed.

In a first step of the process, the directional antenna array may becontrolled such that it has an omni-directional gain pattern. In thismode, when an incoming transmission is first received, certainidentification parameters of an initial portion of the signal aredetected. For example, these may be a source identifier encoded in apreamble portion of a Media Access Control (MAC) layer portion of awireless Local Area Network (LAN) signal.

If the received signal has been previously detected, the controller willsteer the directional antenna to a last known best direction forreception of further portions of the particular detected signal.

If the received signal has not been previously detected, then thecontroller scans the directional antenna to determine a directionsetting that provides a best received signal metric. This can proceed,for example, as an angular search of possible antenna angle settings,and testing a received signal metric for each candidate direction. Thereceived signal metric may, for example, be received signal strength,bit error rate, noise power, or other comparable measure. Once the bestdirectional setting for the antenna is determined, that setting is savedfor future use in receiving the identified signal.

As further portions of the same signal are received, such as payloadportions of the data frame which follow a preamble portion, thedirectional antenna array can be operated to continue to scan potentialnew angles, continuing to look for the best signal metric in a directivemode all the time. Once a signal transmission is concluded, the lastknown best angle for that signal, along with an identification of thesignal, for use in future reception of that same signal.

In a second embodiment, the invention also employs both theomni-directional and directional modes of the antenna, as in theprevious embodiment. In a first step of this process, the antenna arrayis set to an omni-directional mode. A first portion of a received signalis then examined, to determine when a link layer establishment message,such as a Request to Send (RTS) message is received. After an RTS isdetected, identification information for the sender of the RTS is usedto determine a last known angle of arrival. The array is then steered tothis direction for subsequent transmission of, for example, a Clear toSend (CTS) message. A follow-on step may be employed when anacknowledgement of the CTS is then listened for; if the CTSacknowledgement is received, then it is known that the antenna issteered to a proper direction. However, if an acknowledgement of the CTSis not received, it is assumed that the antenna angle must bere-established through scanning candidate angles.

The foregoing embodiment is particularly useful in an access node orother central base unit.

Yet another embodiment of the invention can use the array as follows. Aninitial link layer transmission, such as a Request to Send (RTS) may besent to an intended receiver in a directional mode. This embodiment isparticularly useful where a sender has stored information as to a likelydirection for the intended receiver. The unit then waits to receive aClear to Send (CTS) indication in a receive mode with the antenna set tothe same angle.

If the CTS is received, then it is assumed that the direction iscorrect, and a link layer connection is established.

However, if the CTS is not received within a specified time, thecontroller resets the array to an omni-directional mode, and attemptsagain to establish the link layer connection.

When the invention is deployed in a peer-to-peer network, it may also beused in connection with a device that is responsible for relayingmessages from a first node to a second node. This functionality is ananalogous to a router function in a wireline Internet Protocol (IP)network. In such an application, during the detection process, the angleproviding the best received signal metric was recorded during thereceive mode for a number of nodes in the networks as described above.Therefore, whenever a message is received from a first node that needsto be relayed to a second node, if signals have already been receivedfrom that second node, then the recorded direction of its best receptionis retrieved and used when the antenna array is used to transmit thesignal to the second node. Storage of the best antenna angle forpropagation to neighbor nodes can be handled by control functions in amanner that is analogous to other router lookup table functions, such asbeing contained in a lookup table entry associated with IP addresses.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a system in which the invention isimplemented.

FIGS. 2A and 2B provide examples of Media Access Control (MAC) layerdata frames or messages that may be used to format transmitted signals.

FIG. 3 is a sequence of steps performed by an antenna controller inorder to process received signals according to a first embodiment.

FIG. 4 is a process diagram for the antenna controller according to asecond embodiment.

FIG. 5 is yet another process which the controller may perform.

FIG. 6 illustrates a message and its acknowledgement.

FIG. 7 is a sequence of steps using acknowledgement suppression toconfirm antenna angle setting.

FIG. 8 is a sequence of steps using contention-free periods to confirmantenna angle setting.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 is a high level block diagram of a wireless data communicationnetwork 10 in which the invention may be deployed, such as network forproviding wireless connectivity between a number of end nodes 12 and adata network such as the Internet 18 through access point equipment 14.

Specifically, a first wireless Local Area Network (LAN) 11-1 formed bythe nodes 12-1-1, 12-1-2, . . . 12-1-n. These nodes 12-1 communicatewith each other and a first access point 14-1 using specially formattedradio signals. A directional antenna array 20-1 is used with the accesspoint 14-1 in the first wireless LAN 11-1. The access point 14-1 isresponsible for converting received radio frequency signals to theirappropriate wired format such as the TCP/IP format suitable for Internetcommunications through a gateway 16-1. The gateway 16-1 may be a router,switch, or other internetworking device.

A similar second wireless LAN 11-2 involves the nodes 12-2-p, antenna20-2, access point 14-2, and gateway 16-2.

Each of the nodes 12 include a remote station which is typically aportable Personal Computer (PC) equipped with a wireless networkinterface card (NIC). Other types of computing equipment such asPersonal Digital Assistants (PDAs), desktop computing equipment, andother networkable devices are possible.

The access point (AP) 14-1 acts as a sort of bridge between the wirelessnetwork 10 and wired networks such as the Internet 18. The access point14-1 acts as a base station for the physical layer signaling used in thewireless network, aggregating access for multiple wireless nodes 12-1-1,. . . 12-1-n onto the wired network. The access point 14 usuallyconsists of radio receiver and transmitter equipment and a wired networkinterface such as an IEEE 802.11 Ethernet interface. If the access point14 is to provide connectivity to other networks, it may typicallyinclude bridging software conforming to, for example, 802.1 BridgingStandard, and other software such as firewalls and the like. Ittherefore acts as a router or bridge, from the perspective of higherlayer data networking protocols.

In addition to standard wireless LAN signaling equipment, the accesspoint 14-1 also contains a table 25 which is capable of storingidentification information for the nodes 12 such as a unitidentification and an associated antenna setting parameters, such as anangle. An array controller 30 that permits steering of the particulardirection of the antenna 20-1 such as by specifying an angle. Signalreceiving equipment in the access point 14-1 also contains detectioncircuits that are capable of determining a received signal metric, suchas Received Signal Strength Indication (RSSI), Bit Error Rate (BER),noise power level, or other such measures of receive signal quality.

FIGS. 2A and 2B illustrate the format of a message or frame structuresuch as described in the wireless LAN specification IEEE 802.11b. Themessage consists of a Media Access Control (MAC) layer preamble, header,and payload portion or Protocol Specific Data Unit (PSDU). The messagesin IEEE 802.11 may be either a long preamble-type as used in theconnection with the message shown in FIG. 2A, as well as the shortpreamble-type as shown in FIG. 2B. The different frame formats areassociated with supporting different data rates. The frame format shownin FIG. 2A uses either Double Binary Phase Shift Keying (DBPSK) orDouble Quadrature Phase Shift Keying (DQPSK) encoded at, respectively, 1Mbps or 2 Mbps to modulate the payload portion. The frame format in FIG.2B utilizes DQPSK to realize data rates of 5.5 Mbps or 11 Mbps.

Note also that for both frame formats, the preamble and header portionsof the frame utilize a more robust encoding scheme than the data payloadportions. This permits more reliable detection of the header andpreamble in the presence of noise.

The preamble of either formats shown in FIG. 2A or 2B include anindication of the particular senders, such as in the SFD portion.

FIG. 3 illustrates a flow chart of a process for receiving wirelessnetwork signals in accordance with the invention. The process isperformed in an access point 14 as it receives signals from nodes 12,and may typically be carried out during physical layer processing.

From a first idle step 300, the antenna 20 associated with therespective access point 14 is initially set into an omni-directionalmode. In this omni-directional mode, a state 320 is then entered inwhich the preamble portion and/or header of a received signal isdetected. In state 330, the initial portion of the received signal isexamined to identify it uniquely. If the received signal is unknown,e.g., the node 12 which originated the signal has not been seen before,the antenna is then set in an angle search mode in state 322. In thismode, the antenna 20 is therefore stepped through a sequence ofdirectional angles to find a direction of maximum received signalstrength, signal quality, lowest Bit Error Rate (BER) or other signalquality metric. In state 323, when this angle is determined, it isrecorded and associated with the device identification information, suchas a table entry 25 associated with that device. The table as shown inFIG. 1 may be kept by the access point 14 as part of its message routingtable.

In any event, the access point 14 may then enter a state 324 in whichduring active receptions, the optimum angle is continuously adjustedwhile receiving the payload data portion of the frame. If reception ofthe frame is then lost or otherwise completed, then the last best knownangle is recoded in the table, and processing returns to the initialstate 310.

If from state 330 the signal was able to be identified, e.g., a signalhas been previously received from the transmitting node 12, thenprocessing proceeds to a state 325 in which the last known angle islooked up in the table 25. This last known angle is then used by thecontroller 30 to steer the array to the last known position. The arraythen remains in this last known position at least for reception of thepayload portion of the signal in state 326. From there, the state 324may continue to be entered as the payload portion is being receivedwhereby the angle is continuously adjusted while it is active and anyupdates are then recorded in the table 25.

The state 328 may be entered from state 326 if the unit is in a relaymode, where the best received angle may be used a subsequenttransmissions to that same node.

FIG. 4 is a diagram of a slightly modified process that may also be usedaccording to the present invention. The number of steps of the processin FIG. 4 correspond, more or less, to the steps of FIG. 3. For example,from a first idle step 300, the antenna 20 is initially set in step 310to an omni-directional mode. However, in this embodiment higher layerlevel signaling is examined. For example, in step 315, a Request to Send(RTS) message is detected such as at a link layer. In step 330, themessage is again examined to see if the originator has a knownidentification. If so, steps 325 and 326 proceed as previously where thelast known angle associated with that sender is determined in step 325and the antenna 20 is steered to the last known angle in step 326. Inthis instance, the unit will then send a Clear to Send (CTS) message instep 340 with the antenna now set to the last known angle.

If however, back in step 330, if the identification of the detected RTSis not known, then an angle search proceeds in state 322 and the ID andangle of the best reception state is recorded in step 323. Step 324continues as previously where the angle may be adjusted while activepayload data is being received. Step 345 may be entered when the signaldetection is lost and/or an end of message (EOM) is received.

Returning attention to an instance in which the last known angle issteered to in state 326, a Clear to Send (CTS) message is sent step 340.Next, a CTS acknowledgement is waited for in step 342. Theacknowledgement would typically be received within a predeterminedamount of time or otherwise a time-out condition exists. If theacknowledgement is received, then the specified angle is presumed to beokay and in state 344 and then processing may proceed to step 324.However, if a time-out does occur in step 342, then it is presumed thatthe angle to which the antenna 20 was steered is bad and therefore theangle search state 322 must be entered.

The foregoing methods are particularly useful in applying an applicationto an access node or central base station unit wherein it is intended toservice a number of remote subscriber units.

However, another embodiment of the invention can be applied to advantagein a subscriber unit as follows. This set of operations is illustratedin FIG. 5. In a first step 500, the antenna is set to a directionalmode. For example, it is typically common that the subscriber will havethe given information with respect to its candidate direction in whichthe base station exists. In step 510, a Request to Send (RTS) message issent in a directional mode. In step 520, if a Clear to Send (CTS)message is received back from the base station, then it can be presumedthat the antenna direction setting is okay in step 522 and the linklayer communications may proceed in step 524.

If however, in step 520 there is no CTS received within a time-outperiod, then it is presumed that the antenna is incorrectly set. Thus,an omni-directional mode is entered in step 528 and the RTS message issent in step 540. Processing then proceeds from that point similar tothat described in FIG. 3 and/or FIG. 4, i.e., an angle search isperformed to properly set the antenna in step 544 and the setting isrecorded in step 548.

FIG. 5 illustrates a sequence of higher level messages that may be sentin a typical network computer environment. Specifically, a sourcestation which may either be the access point 14-1 or remote stations 12,sends a message 610. The message 610 may consist of one or more packetsthat have the previously described preamble, header, and payloadportions. The message may be a relatively detailed message or may be arelatively simple message such as a request to set up a connection andsend further information.

In response to receipt of the message 610, the destination station isexpected to return and acknowledgement message 612. This acknowledgementmessage 612 may have a preamble portion and a header portion thatspecifically has a header or payload portion that is a knownacknowledgement (ACK) format. The higher layer protocol may be, forexample, implemented at a link layer.

The present invention may make use of these higher layer protocol unitsto invoke other protocols to help train the antenna.

The acknowledgement message 612 is sent upon receipt of a proper message610 at the destination station. However, situations may also exit 614 inwhich no acknowledgement is sent from the destination. This is typicallydone if the message is not received within a predetermined period oftime at the destination. In that manner, the source will know to attemptto retransmit the message 610. This acknowledgement protocol is typicalof higher layer protocols in widespread usage in data communicationnetworks typical of the Transmission Control Protocol/Internet Protocol(TCP/IP) protocol used in Internet data communications.

It may become necessary to use the higher layer protocol information incertain circumstances wherein the physical layer protocols do not permittime to demodulate the data frame and/or do not contain identificationof the sending station in the preamble portion. Such protocols present aproblem in that there is no way to know transmitter ends without sometype of demodulation taking place. However, there is, in turn, no timein which to or there is no time in which to demodulate the signal. Forexample, it may not be possible to determine quality of a receptionuntil after an entire frame is processed. This may depend upon thespecific coding used for the frame. In addition, certain protocols mayuse preamble portions that are too short in duration to identify thebest direction in time for this antenna array to be affectively steeredto the appropriate direction. For example, 802.11B Standard ispotentially acceptable in this regard. However, protocols such as the802.11A Wireless LAN Standard may not provide sufficient durationpreamble. In addition, the wireless LAN protocols work on a similarradio link protocol that is similar to Ethernet. In particular, apositive acknowledgement radio link protocol is used. For example, ifcorrectly received packets are acknowledged whereas incorrectly receivedpackets are not. Thus, the non-acknowledgement test can be performed ata radio link protocol layer and/or higher level layers.

Essentially, the process is shown as in FIG. 6. For an initial idlestate 600, tenant array 20 is first steered to an omni-directionalstate.

In a next state 712, a transmission is received. When this packet isreceived correctly, a state 714 is entered in which the acknowledgement612 that would normally be sent is suppressed. Therefore, the unitenters a mode in which no acknowledgement is sent 614. This permitsentry to a state 716 in which the angle for the antenna may be set. Thesuppression of the acknowledgement in state 714 causes a second receiptof the packet in state 718. In this second receipt in state 720, thereceived quality is compared. If the received quality is not adequate,then the process loops back to state 714 in which the acknowledgement issuppressed once again. Step 714 through 720 are continuously executeduntil an acceptable received packet quality is determined in state 720.When this occurs, control passes to state 722 in which anacknowledgement is presently sent. The set angle is then recorded withthe identification of the unit for subsequent communication with thatunit.

It should be understood that in certain instances upon receipt of thepacket in 712, if the identification of the unit can be determined, thenthe angle may be more appropriately set upon the second try in state716, such as in shown in FIG. 3. For example, if the identification ofthe remote unit can be made from the received packet in state 712, thenthe angle search associated with step 714 through 720 can proceed moreexpeditiously.

What is important to note here is that the higher layer protocol isbeing used to force a retransmission of a packet for the purpose ofoptimizing the antenna array setting. Other protocol attributes or unitscould be used for similar results. For example, a contention-free windowcan be set up by certain protocols using a so-called PCF or HCF mode. Inthe PCF mode, a means is provided for discovering the best angle thatcan be controlled by an access point as to which units will betransmitting during a certain period of time. Thus, the identificationof the unit being known in advance, the antenna can be steered to thelast known direction for the communication prior to its receipt. Thus,the control messages may be set up while an omni-directional mode thenwhen transmitting to the remote unit, the directed mode can in HCF orHybrid Coordination Function can be determined.

Turning attention more particularly to FIG. 8, an 802.11 access point 12has essentially two modes, including a distributed correlation function(DCF) mode 810 and a point coordination function (PCF) mode 830. In theDCF mode, communication is basically contention-based whereby any one ofthe subscriber units 12 may be allowed to attempt to send messages tothe access point 14 at any point in time. The PCF mode 830 is enteredinto from time to time to provide a mode in which contention-freecommunication is possible. Thus, while in the PCF mode, the systemguarantees to a particular subscriber unit 12 that it will be able tohave exclusive access to the airwaves and send messages to the accesspoint 814, free of any collision with other subscriber units 12.

Thus, in one state 812 associated with DCF mode 810, the access point 14receives requests on a sporadic basis from particular subscriber units12 to be granted contention-free areas (CF) at a later time. Eventually,the PCF mode is entered in state 830. In this state, the antenna isfirst sent to an omni-directional mode 832. In a next state 834, abeacon signal is sent to all subscriber units 12 to indicate that thePCF mode is being entered into. This is a signal to all units to listenfor upcoming polling information to determine if they will be granted acontention-free period. A poll signal is then sent out at state 834. Aresponse to the poll signal in state 834 determines a particularidentifier of one of the subscriber units 12 which is to be grantedcontention-free access during the PCF mode. It should be understood thatduring any given PCF mode, a number of different subscriber units 12 maybe granted exclusive use or may be granted a contention-free period oneafter the other.

From its schedule of subscriber units 12 that have requestedcontention-free periods, the access point in state 834 polls the firstsuch unit on its list. The poll message is sent by steering the antennato the last known location or correct angle for the particularidentified subscriber unit 12. This particular PCF message is then sentin step 838 as a contention-free message. Steps 834 through 838 are thencontinuously executed until each of the subscriber units that hadrequested a CF eventually be granted their turn at a contention-freeperiod. Upon each subsequent such subscriber unit 12 being accessedduring the contention-free period, the antenna will be steered to itsrespective appropriate direction in the state 836 prior to sending theassociated PCF message for the particular subscriber unit 12. At the endof the contention-free processing in state 838, the access unit may thensteer the antenna array 20 back to an omni-directional mode so that in astate 840, a contention-free period end message may be sent to all ofthe subscriber units so that they may understand that the end of PCFmode has been reached and that the system is then now returning to a DCFmode in state 810.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

1. A method for operating a communication network in which a first andsecond station exchange information using wireless physical layersignaling, comprising the steps of: setting an omni-directional mode foran antenna array; receiving a transmission at the first station from thesecond station; determining an identification of the second station fromthe received transmission; steering the directional antenna array in thedirection of the last known location for the identified unit; and ifidentification of the second station is not determined, steering thedirectional antenna through a series of candidate directions todetermine an optimum direction for receipt of communications from thesecond station.
 2. A method as in claim 1 wherein the directionalantenna is a steerable array of multiple antenna elements.
 3. A methodas in claim 1 wherein a first portion of the transmission is a preambleof a data frame.
 4. A method as in claim 3 wherein the preamble portionof the data frame is encoded with a more robust modulation scheme thanthe following portions of the transmission.
 5. A method as in claim 3wherein the preamble portion may have one of a plurality of possiblepreamble formats.
 6. A method as in claim 3 wherein the preamble portioncontains sender identification and the payload is regarded assubsequently sent frames.
 7. A method as in claim 3 wherein the preambleportion is a complete data frame containing identification of a sender.8. A method as in claim 1 wherein antenna array parameters areassociated with the identification of the second station.
 9. A method asin claim 8 wherein the unit identification and antenna parameters arestored in a table associated with a network layer address associatedwith forwarding communications between the first and second station. 10.A method as in claim 9 wherein the network address is an InternetProtocol address and the first station performs routing functions fornetwork layer messaging.
 11. A method as in claim 8 additionallycomprising the step of: if it is not possible to determine anidentification of antenna parameters from the identification of thesecond station, searching for an antenna parameter setting to determinean optimum direction for receipt of communications from the secondstation.
 12. A method as in claim 1 wherein a robust, lower codedmodulation type is used during transmission of a first portion, and ahigher coded modulation type is used during a later portion of thetransmission from the second station.
 13. A method as in claim 1 whereinthe first station is an access point and the second station is a remotestation.
 14. A method as in claim 1 wherein the first station is aremote station and the second station is an access point.
 15. A methodas in claim 1 wherein a first portion of the transmission is a firstpacket.
 16. A method as in claim 15 additionally comprising the step of:during a sequence of known series of transferred packets, steering theantenna array without concern for packet loss.
 17. A method as in claim16 additionally comprising the step of: employing a packetacknowledgement mechanism to recover any lost data.
 18. A method as inclaim 16 additionally comprising the step of: relying on a radio linkcontrol protocol (RLP) mechanism to recover lost packets.
 19. A methodas in claim 1 wherein a subsequent transmission is a later portion of adata frame.
 20. A method as in claim 1 wherein a subsequent transmissionis a later transmitted packet.
 21. A method as in claim 1 wherein thestep of determining identification of the transmitting second stationoccurs from a portion of the transmission received while the antenna isoperating in the omni-directional mode.
 22. A method as in claim 21wherein identification is contained in a higher coded portion of thetransmission.
 23. A method as in claim 1 wherein the directional antennais steered to the last known direction before later portions of thetransmission begin.
 24. A method as in claim 1 additionally comprisingthe step of: after the optimum direction is determined, storing thedirection information, together with the unit identificationinformation, for use in subsequent processing of signals received fromthe identified unit.
 25. A method of operating a communication system inwhich a first and second station exchange information using wirelessphysical layer signaling, and the first station making use of adirectional antenna, the method comprising the steps of: determiningwhen a wireless signal is being received from the second station at thefirst station; utilizing messages at a protocol layer higher than thephysical layer to control transmission and retransmission of data from aspecific second station; using the transmitted messages at higher layerprotocols to steer the antenna array; and wherein the protocolattributes are used to force a retransmission of the data packet for thepurpose of optimizing the antenna array steering.
 26. A method as inclaim 25 wherein the protocol attribute is an acknowledgement (ACK)returned from the first station to the second station.
 27. A method asin claim 26 wherein the acknowledgement message is suppressed in orderto force a retransmission from the second station to the first station.28. A method as in claim 27 wherein the acknowledgment suppression isperformed only upon one of a number, N, of transmissions to provide forreduction in duty cycle of the adaptation of the antenna.
 29. A methodas in claim 26 additionally comprising the step of: after the firstacknowledgement suppression, identifying the second station from whichthe transmission is being received to determine an angle for the antennabased upon the history of past transmissions from the specific secondstation.
 30. A method as in claim 25 wherein the protocol units utilizeRequest to Send (RTS) and Clear to Send (CTS) protocol data units toensure transmission of frames from a specific second station.
 31. Amethod as in claim 25 wherein the protocol units are Point CoordinationFunction (PCF) entities that only request a specific second station totransmit.